Ron, thanks for the information.

I copied and pasted your equation into my spreadsheet, and placed the data
in the indicated columns to avoid any typo errors. I used the second example
as I only am solving for Y, with X being known.

What I find is that for the smaller values of X, the returned values of Y
are quite accurate, but a small error creeps in as X increases. This is
probably not surprising due to the increase in curvature at higher values.

However, I find that I cannot input any value of X greater than 5,879,999.
If I do the value returned is #DIV/0!

This I do not understand and I do need to use all of the table data.

Any thoughts here?